It may be expected that, in the future, for stationary applications, such as wind power plants, as well as in vehicles, such as hybrid or electric vehicles, new accumulator systems will be increasingly used which will be subjected to very high demands with respect to their reliability. The backdrop of these high demands is that a failure of the accumulator may result in a failure of the entire system. For example, a traction battery failure in an electric vehicle results in a so-called “car breakdown.” This may even result in safety problems. For example, accumulators are used in wind power plants, in order to protect the plant from improper operating conditions during strong winds by readjusting the rotor blades.
For providing high energies and outputs, multiple accumulator lines 64, 66 are also switched in parallel to one another. The schematic circuit diagram of such an accumulator 40 is shown in FIG. 2.
In order to be able to disconnect accumulator 40 from an electrical consumer, e.g., a vehicle electrical system, two power switches, such as contactors 42, 44, are typically provided. When switching on the two contactors 42, 44, a substantial current 46 would, however, flow into DC link capacitor 48, so that a so-called precharging contactor 50, 52 and main contactor 54, 56, which is attached to the other accumulator pole, are initially switched on. Precharging contactor 50, 52 usually has a protective resistor 58, 60. As a result, DC link capacitor 48 is initially charged with a delimited current 46. As soon as voltage 62 at DC link capacitor 48 is sufficiently high, main contactor 42, 44 is switched on. Conventionally, such a circuit 63 is used for both accumulator lines 64, 66 independently from one another.
However, the costs of the circuit breakers in main contactors 42, 44, 54, 56 are very high. Furthermore, it appears that when both precharging contactors 50, 52, or a main contactor 54, 56 and a precharging contactor 50, 52, which is associated with the other accumulator line, are switched on simultaneously, a compensating current, which is converted at precharging resistors 58, 60 into lost heat, flows via precharging contactors 50, 52 and the associated resistors 58, 60 between the two accumulator lines 64, 66.